Magnetically guided myocardial treatment system

ABSTRACT

A magnetically topped catheter is used to tunnel into the myocardium for cardiac treatment.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part of U.S. patent application Ser. No. 09/398,686, filed Sep. 20, 1999, now U.S. Pat. No. 6,562,019, issued May 12, 2003, the disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

[0002] The present invention is related to the medical treatment of the myocardium and more specifically to devices for accessing the myocardium and to techniques for magnetically guided myocardial interventions.

BACKGROUND OF THE INVENTION

[0003] Various diseases exist that require precise access to the heart muscle. Current treatment modalities have been limited by the ability to direct and hold treatment devices in the proper location in a beating heart. Consequently, major open surgical interventions are common where a minimally invasive approach would be preferable. One such procedure is myocardial revascularization and the inventions are described in that context.

[0004] For example, patients who exhibit ischemic heart disease and who experience angina can be treated by perforating the wall of the ventricle. It is not entirely understood why this form of injury improves the cardiac performance of the patient. Some evidence suggest that the healing response to the injury causes new blood vessels to form and increases the size of existing blood vessels. The additional blood flow relieves the symptom angina.

[0005] The first myocardial revascularization experiments were performed with a laser, which was used to perforate the heart from the “outside” of the heart. In general, the laser energy was applied to the exterior wall of the ventricle and activated. In use, the laser energy burns and chars a hole in the heart wall. The blood pool inside the heart prevents further injury to structures within the heart.

[0006] More recently, it has been proposed to revascularize the heart wall through a percutaneous transluminal approach. See for example Nita, U.S. Pat. No. 5,927,203, incorporated herein by reference. This technique can be used to place a catheter against the endocardial surface of the heart. However, the heart wall is in constant motion and this relative motion renders creation of the lesion problematic.

[0007] In general, both improved devices and techniques are needed to advance this therapy.

SUMMARY OF THE INVENTION

[0008] The methods and devices of the invention are useful in a variety of settings. For purposes of illustration, the invention is described in the context of myocardial revascularization which is one instance where the catheter is magnetically navigated to a site near a wall of the heart. Other examples of treatments include the repair of septal defects and heart biopsy. It is anticipated that some forms of cardiomyopathy may respond to therapies delivered with these tools as well. For this reason it must be understood that the devices and methods can be used in a variety of contexts within the body.

[0009] A magnetically navigable and controllable catheter device is deployed at the heart wall and this device tunnels into the myocardium. Any of a variety of canalization techniques can be used to tunnel into the heart wall causing mechanical disruption of the tissues, including mechanical needles and RF energy sources as well as direct laser and heated tips. In a preferred embodiment, the catheter device guided by externally applied magnetic fields that are created by a magnetic surgery system (MSS). The MSS applies magnetic fields and gradients from outside the body to manipulate and direct medical devices within the body. The catheter devices of some embodiments of the present invention include magnetic elements that respond to the MSS field or gradient. In general, the physician interacts with a workstation that is associated with the MSS. The physician may define paths and monitor the progress of a procedure. Fully automatic and fully manual methods are operable with the invention.

[0010] Although several energy sources are disclosed that can be delivered by the catheter through its distal tip, an RF heated tip is preferred since it can be used both to cut and to coagulate tissues depending on the delivered energy level. This feature is shared with laser-heated tips and thermal catheter technologies but RF devices have a greater history of use for coagulation.

[0011] The proposed methods of the invention can be used to move the catheter device both along and across the muscle planes within the heart tissue so that a complex should pathway or “tunnel” can be created. This structured shape can be used to retain “implant” materials such as growth factor. Growth factor or other drugs may be embedded in or on absorbable material. In some instances it may be desirable to combine the drug with a magnetic particle sot that the gradient and fields can be used to position and retain the drug in the tissue. For example, the lesion can be in the form of a “blind” hole and the drug can be left behind in the wound and retained magnetically inside the tissues.

[0012] For purposes of this discussion, the term “ablation” or “lesion” should be considered to include thermally damaged tissues, eroded and charred tissue by other processes that destroy or remove tissue. Typical devices to carry out this “injury” include mechanical, RF, electrical, thermal, optical, and ultrasonic means. Throughout the description the wound is referred to as a tunnel in recognition of its shape.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Throughout the various figures of the drawing identical reference numerals are used to indicate identical or equivalent structure, wherein:

[0014]FIG. 1 is a schematic of a heart showing two surgical approaches;

[0015]FIG. 2 is a representation of a step in the method;

[0016]FIG. 3 is a representation of a step in the method;

[0017]FIG. 4 is a representation of a step in the method;

[0018]FIG. 5 is a representation of a step in the method;

[0019]FIG. 6 is a representation of a step in the method;

[0020]FIG. 7is a representation of a step in the method;

[0021]FIG. 8 is a schematic of an exemplary thermal catheter;

[0022]FIG. 9 is a schematic of a mechanical revascularization catheter;

[0023]FIG. 10 is schematic of a RF revascularization catheter;

[0024]FIG. 11 is a representation of a serpentine path through the heart tissue possible with the methods and apparatus of this invention;

[0025]FIG. 12 is perspective view of one embodiment of an apparatus useful in the methods of this invention;

[0026]FIG. 13 is a side elevation view of another embodiment of an apparatus useful in the methods of this invention.

[0027] Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0028]FIG. 1 shows a schematic heart 10 located within the patient interacting with a magnetic surgery system or MSS 12. Two different surgical approaches are shown in the figure represented by catheter 16 and catheter 22.

[0029] The MSS system 12 includes a magnet system 14, which can generate controlled fields and gradients within the patient. The MSS 12 may also optionally include a localization system 17, which can be used to find the location and direction of the catheter tip within the body. The MSS 12 may also optionally include an imaging system 15, which can be used to display the real time location of the catheter with respect to the tissues. The imaging system 15 can also be used to collect preoperative images to guide the procedure. A companion workstation 18 is interfaced with these systems and controls them through the workstation 19. It should be noted that the energy source for the revascularization catheter is under the control of the MSS as well so that the therapy is integrated through the workstation. In general, the advancement of the catheter can be performed directly by the physician or the process may be automated through the workstation. For these reasons the invention contemplates both fully manual and fully automatic procedures mediated by the MSS.

[0030] Catheter 16 is depicted in a ventricle for a therapeutic intervention. This catheter shows a percutaneous transluminal access of the ventricle. Catheter 22 is shown in contact with the ventricle through an incision in the chest. This catheter shows a pericardial access to the epicardial surface of the heart 10. Catheters may also approach the heart through a site in the coronary tree. Although three different approaches are shown or described, the remainder of the description is disclosed in the context of the preferred transluminal approach for simplicity and clarity of disclosure. It should be recognized that the devices and procedures might be used in the other approaches as well.

[0031]FIG. 2 shows a catheter 16 in contact with the endocardial surface 11 of the heart. The distal tip 24 may include a magnetic or magnitizable material that interacts with the MSS field 26. One distinct advantage of this approach is that the applied field creates a force that holds the tip 24 in contact with the moving myocardial wall 28. Once an appropriate starting position has been established the tip 24 is activated through the workstation 19 and the catheter enters the myocardial wall 11 seen best in FIG. 3.

[0032]FIG. 3 shows the tip 24 turning under the influence of the MSS. A primary entrance axis is defined and shown in the figure as axis 36 while the instantaneous direction of travel is shown as path 38. It is a property of the device 16 that can track in the tissue and turn from an entry path through approximately 90 degrees within the distance of the heart wall.

[0033]FIG. 4 is an example of the use of the system to treat an infracted region 17 of the heart by encircling it with an ablation path within the wall 28 of the heart. In use, the MSS system is used to define the circular path indicated in the figure as path 19.

[0034]FIG. 5 shows the catheter 16 being used to define a very complex path within the heart wall 28. The MSS defines the arcuate path 21 and the magnetic tip 24 of the catheter 16 follows the path. In use, the ablation energy source is sufficient to tunnel in the tissue. Ablation wounds for this nature may be used to treat ‘hibernating tissue’ with drugs and the like.

[0035]FIG. 6 shows a guided intervention with the myocardial tissues. The MSS 12 can be used to define a path for the tip 24 of the catheter 16. A simple straight through path is depicted as path 38 this path takes the catheter 16 tip 24 completely through the block of tissue 11. The curved path is shown as path 36 which turns within the tissue so that the tip 24 is retained in the myocardium. In the illustration the tip 24 is following the curved path 36. In this example the tip, enters the tissue at an approximately orthogonal angle and remains within the myocardial tissues and creates a blind “wormhole” lesion or path. A lumen 40 in the catheter body 42 can be used to deliver a drug such as growth factor to the site of the injury. Other candidate drugs contemplated within the scope of the disclosure include VEGF vascular endothelial growth factor aFGF acidic fibroblast growth factor. It is believed that the uptake of the drug will be effective and result in the rapid development of new vessels. FIG. 6 shows a set of wormhole tracks, which share a common entry point 42. In operation, the catheter body may be retracted along the track and repositioned with the MSS to create a complex series of lesions that share the common entry point forming a “star” shaped system of tunnels. Upon retraction out of the tissues the power level at the tip 24 can be reduced and the tip can “cauterize” or seal the opening entry point 42.

[0036]FIG. 7 shows a preferred therapy where a RF heated catheter is used to create a “wormhole” lesion under the control of the field 26. During withdrawal of the catheter deposit drug coated magnetic particles typified by particle 60. The distal tip 52 cauterized the tissue on the exit path coagulating tissue shown as plug 63.

[0037]FIG. 8 shows an illustrative but preferred catheter 16. The preferred tunneling energy is a heated tip 24 which may accomplish with either radio frequency (RF) or laser energy through an optical fiber 33 from the energy source 21.

[0038] Localization coils 30 or the like in the catheter 31 may be used with the MSS to reveal the real time location of the catheter. Real time biplane fluoroscopy can also be used to show the physician the location of the device against the wall. The coils or other structures may be included to increase the radiopacity of the catheter tip.

[0039]FIG. 9 shows a mechanical catheter with a retractable needle 51, which may be manipulated through the proximal wire 56. In use, the needle can be used to pierce the heart wall. The catheter body 57 includes an optional lumen 40, which may be used to deliver a drug during the therapy.

[0040]FIG. 10 is an RF heated bipolar catheter using a distal electrode tip 52 with a proximal indifferent electrode 53 to supply heat to the tissues. An optional lumen 40 is shown for the delivery of a drug. One advantage of the RF catheter is the ability to lower the energy delivered to coagulate tissues.

[0041]FIG. 11 is a representation of a serpentine path 100 through the heart tissue 102 possible with the methods and apparatus of the various embodiments of this invention. As shown in FIG. 11, the serpentine path 100 has a generally “S” shape, and preferably contain at least two bends of greater than 90°. The complicated path 100 helps retain substances delivered therein, but was difficult if not impossible to form with the apparatus and methods of the prior art.

[0042] A device useful in the methods of this invention is indicated generally as 150 in FIG. 12. The device 150 has a proximal end (not shown) a distal end 154, and a sidewall 156 extending therebetween defining a lumen 158 preferably extending the length of the device. An electrode 160, with a dome shape, is disposed at the distal end, and is provided with RF energy via lead 162. There as preferably a magnetically responsive element 164 in the distal end portion of the device 150. The element 164 is either a permanent magnetic material such as a neodymium-iron-boron alloy, or a permeable magnetic material. The material is selected, and the element is sized and shaped so that in an applied magnetic field, such as that from a MNS as discussed above, a magnetic moment is created orienting the distal end of the device in a selected direction. A tube 166 extends through the lumen, through a passage in the magnet element 164, and opens to a passage in the electrode 160, so that materials can be delivered into the paths created by the distal end of the device 150.

[0043] In operation the distal end of the device is navigated to the heart, and pressed against the heart wall. The RF energy is applied to the electrode 160 to form a hole in the heart tissue, by magnetically orienting the device 150 (by changing the external field direction) and advancing the device (either manually or with a motoized advancer) tunnels can be formed. However, because of the unique control permitted with magnetic navigation together with the very small size and extreme flexibility of the device, the paths formed by the device can take on complex shapes, which allowed for wider dispersal of agents, and improved retention of those agents. In particular the present invention permits the formation of serpentine paths, such as path 100 in FIG. 11.

[0044] Another device useful in the methods of this invention is indicated generally as 200 in FIG. 13. The device 200 has a proximal end (not shown) a distal end 204, and a sidewall 206 extending therebetween defining a lumen 208 preferably extending the length of the device. The distal end 204 of the device 200 preferably has a generally rounded or dome-shaped configuration. There as preferably a magnetically responsive element 214 in the distal end portion of the device 200. In this preferred embodiment, the element 214 is a set of three mutually perpendicular coils 216, 218, and 220, that can be selectively energized to create a magnetic moment, preferably in any direction. Pairs of lead wires (not shown) can independently power each of the coils. Thus, when a magnetic field is applied to an operating region containing the device 200, the distal end 204 of the device can be oriented in any direction by the controlled application of currents to the coils 216, 218, and 220. A magnetic field an be applied with a MNS, but the magnetic field could also be provided by a MR imaging system. An MR imaging system could provide a particularly strong magnetic field that is useful in navigating. The navigation of a medical device in an operating region with the aid of an externally applied magnetic field, such as that provided by an MRI device, by using a controllable variable magnetic moment in the device tip has been proposed, and is in fact the subject of Kuhn, U.S. Pat. No. 6,216,026, Arenson, U.S. Pat. No. 6,304,769, and Hastings et al., U.S. Pat. No. 6,401,723, the disclosures of which are incorporated herein by reference.

[0045] The MR imaging system also provides images of the tissues, so that the distal end 204 of the device 200 can be properly controlled to formed the desired complex paths. Of course, other imaging systems can be used including OCT, OCR, or ultrasound. In stead of, but more preferably in addition to imaging, some localization system can be used to further fix the position of the distal end of the device. To this end the coils 216, 218, and 220 can be used as part of a magnetic localization to fix the position and/or orientation, of the element 214, and thus of the distal end of the device.

[0046] An optical fiber 222 extends the length of the device 200, and is connected at its proximal end to a laser that provides energy for ablating tissue at the distal end of the optical fiber.

[0047] A tube 224 extends through the lumen, and opens to a passage in the distal end 204 of the device 200, so that materials can be delivered into the paths created by the distal end of the device.

[0048] In operation the distal end of the device is navigated to the heart, and pressed against the heart wall. The laser energy is applied to the optical fiber 222 to form a hole in the heart tissue, by magnetically orienting the device 200 (by changing the current in the coils 216, 218, and 220 and/or changing the external field direction) and advancing the device (either manually or with a motorized advancer) tunnels can be formed. However, because of the unique control permitted with magnetic navigation together with the very small size and extreme flexibility of the device, the paths formed by the device can take on complex shapes, which allowed for wider dispersal of agents, and improved retention of those agents. In particular the present invention permits the formation of serpentine paths, such as path 100 in FIG. 11.

[0049] The methods can be used to form passageways in the heart tissue, and or to deliver substances to the heart tissue via the passageways. These substances include stem cells (and particularly Autologous Cultured Stem Cells), gene therapy, VEGF (vascular endothelial growth factor), myoblasts, drugs and other materials and substances. For example, as disclosed in Law, The Regenerative Heart, in Business Briefing:Pharmatech 2002 incorporated herein by references, various treatments for the regeneration of heart tissue as discussed such as va 

What is claimed:
 1. A method for myocardial treatment comprising the steps of: navigating a catheter to a treatment site; displacing the catheter into the tissue at the treatment site directing the tip of the catheter with magnetic fields applied from outside the body; advancing the tip through tissue causing mechanical disruption of tissue forming a tunnel in the tissue at the treatment site.
 2. The method of claim 1 wherein the catheter delivers ablation energy during the advancing step.
 3. The method of claim 1 including the further step of: stopping the advancing prior to the catheter tip exiting the tissue, thereby creating a blind hole tunnel in the tissue.
 4. The method of claim 1 wherein: the directing step causes the tip to orient through an angle of approximately 90 degrees as measured from the entry angle between the tissue plane and the catheter body.
 5. The method of claim 3 further comprising: repeating the steps of claim 3 sequentially while turning the catheter at the entry point, thereby forming a star shaped tunnel in the tissue.
 6. The method of claim 1 further including the steps of: injecting a drug through the catheter into the lesion; withdrawing the catheter from the tunnel.
 7. The method of claim 6 further including the step: sealing the tunnel upon exit of the catheter from the tunnel whereby drug left in the wound is sealed in the tissue.
 8. A catheter comprising: a catheter body having a proximal end and a distal end; a tunneling structure located at the distal end of the catheter body; a magnetic element located proximate the distal tip of said catheter body; for guiding the catheter tip in response to external magnetic fields and gradients.
 9. The catheter of claim 8 further comprising: a lumen extending to the location proximate the distal tip for the delivery of drug to the site of the catheter.
 10. A method of treating the heart comprising the steps of: navigating a catheter to the myocardium; entering the myocardium assisted by the application of externally generated magnetic fields and gradients to create a treatment site; delivering a magnetically bound drug to the treatment site; withdrawing the catheter while retaining the drug of the site with a magnetic field or gradient.
 11. A method of treating the heart comprising: navigating a catheter having a magnetic tip to the myocardium using externally applied magnetic fields or gradients to direct the tip; advancing the catheter into the myocardium at a singular treatment site; injecting a drug through a lumen in the catheter into the myocardium at the treatment site; withdrawing the catheter from the treatment site. 